A new acoustic metamaterial developed by a team at the University of Wisconsin Madison is turning heads and turning objects with nothing but sound.
Presented this week by doctoral researcher Dajun Zhang at the 188th Meeting of the Acoustical Society of America (co-hosted with the 25th International Congress on Acoustics), the innovation centers around a finely engineered metamaterial with a sawtooth patterned surface that responds to precisely targeted sound waves. When submerged or floated in water and hit with audio from surrounding speakers, the material enables movement of attached objects including pushing, pulling, and rotating all without physical contact.
Zhang and his team demonstrated the system’s ability to manipulate a range of lightweight materials like wood, wax, and plastic foam, both floating and fully submerged. In 3D. Using sound alone.
🎯 What makes this possible?
The core tech lies in the material’s acoustic metamaterial properties that is, it’s not just about what it’s made of, but how it’s structured. Metamaterials are engineered to behave in ways that natural materials can’t. In this case, the sawtooth geometry of Zhang’s material allows it to reflect sound in complex, controllable ways.
By varying the angle, frequency, and phase of sound coming from multiple directions, the team can generate specific radiation pressure patterns on the metamaterial’s surface. The result is a fine-tuned force that can move the object to which it’s attached in any direction including rotation.
This isn't acoustic levitation as you’ve seen it with small particles floating in air. This is underwater actuation a potential breakthrough for robotics, medical tech, and industrial assembly in liquid environments.🧪 A manufacturing breakthrough
One of the big bottlenecks in acoustic metamaterials has been fabrication. Producing high resolution surfaces with strong impedance contrast (essential for acoustic control in water) has traditionally required expensive, complex manufacturing.
Zhang’s team developed a low cost, high resolution method that solves this. His process not only achieves the necessary acoustic impedance to contrast sharply with water, but also scales down in size while remaining robust a key for medical and micro robotic applications.> “Current fabrication methods for underwater metamaterials do not provide the resolution or material properties required and are usually very expensive,” Zhang explained. “To solve this, I developed a new method that is not only low cost and easy to implement but also achieves the necessary physical properties.”This innovation lowers the barrier to broader adoption, possibly opening the door for startups and labs looking to experiment with underwater actuation without a six-figure equipment budget.🌍 Reason
There are obvious applications in underwater robotics. Assembly of delicate structures or parts, inspection tasks, or object retrieval could all benefit from remote manipulation that avoids mechanical arms or grippers. This also sidesteps the challenges of cables, tethers, and mechanical contact in complex aquatic environments.
Then there’s the medical angle the human body is ~60% water. Zhang’s vision includes in body applications: steering drugs, manipulating soft medical devices, or even guiding microrobots during procedures all using externally generated sound waves.
Zhang is now focused on creating a smaller, more flexible patch version of the metamaterial. The goal: to embed these patches on tiny or irregularly shaped objects and maintain precise control inside confined, liquid-filled spaces.
🧠 Future potential
✓Underwater drones or robots that can reposition or reconfigure themselves without joints or motors.
✓Medical devices that operate deep in the body without invasive contact.
✓Lab on chip systems where fluids and materials are moved acoustically.
✓Non invasive surgical tools or even acoustic biopsy methods.There’s still work ahead in dealing with noise, turbulence, and chaotic environments, especially in real-world underwater scenarios. But the ability to generate 3D force profiles with nothing but structured sound is a major step toward that future.Let me know if you want the fabrication details Zhang shared during the presentation. Happy to dig deeper.